Instruments for controlling operations, to ensure optimum operating conditions of such operations



Dec. 7, 1965 r. A. BANNING, JR

INSTRUMENTS FOR CONTROLLING OPERATIONS, TO

ENSURE OPTIMUM OPERATING CONDITIONS 0F SUCH OPERATIONS original FiledJan. 8. 1945 4 Sheets-Sheet 1 Ill @W mb bh. 690D .UErAU man:

Dec. 7, 1965 T. A. BANNING, JR 3,221,759

INSTRUMENTS FOR CONTROLLING OPERATIONS, TO

Original Filed Jan. 8, 1945 FIGB.

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ThomasA.Banmng,llr.

Dec. '7, 1965 T. A` BANNING, JR 3,221,759 INSTRUMENTS FOR CONTROLLINGOPERATIONS, TO

ENSURE OPTIMUM OPERATING CONDITIONS 0F SUCH OPERATIONS Original FiledJan. 8, 1945 4 Sheets-Sheet 4 Frequency G-eneromn i Y`Op||e|f S05 `.4574 /527 f v Pi'rch Manual Changer: Wfcremm MBH.

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United States Patent O Claims. (Cl. 1317-18) This application is adivision of my co-pending application for Letters Patent on Improvementsin Instruments for Controlling Operations to Ensure Optimum OperatingConditons, Serial No. 662,542, filed May 29, 1957, and allowed December1l, 1962, now Letters Patent No. 3,- 096,469, issued July 2, 1963; whichapplication, Serial No. 662,542, was a division of my application `forImprovements in synchronizing Systems for Plural Propellers with Pitchand Fuel Control, Serial No. 248,340, filed September 26, 1951, nowLetters Patent No. 2,794,- 507, issued June 4, 1957; and whichapplication, Serial No. 248,340, was a division of my earlierapplication for Improvements 'in Propeller Pitch Control, Serial No.573,382, filed January 18, 1945, now Letters Patent No. 2,569,444,issued October 2, 1951.

This invention relates to improvements in instruments for controllingoperations to ensure optimum operating conditions of such operations,and the like. The following brief statement will explain certain of theoperations which are controlled by instruments embodying my presentYinventive features, and will also show certain of the complexrelationships which are brought into simple operative functions andcontrols to enable attainment of the optimum operating conditions abovereferred to.

Frequently industrial and other operations, such as power generatingoperations, include the inter-relating of two or more operationalfunctions or variables in operations wherein economy of the operation isaffected by either or both such variables. Under such conditions theoverall operation may continue uninterruptedly for the continuousoperation, but the economy of such operation will be affected in mannerdepending on whether such variables are at any given time properlyrelated to each other as affected by the value or speed or otheroperating characteristics of one or another of such variables. Themanner of the effect produced on the overall economy will depend on therelationships of the variables to each other at the time in question.Generally by changing one or the other of the variables with, possiblycorresponding change in another variable or variables, the overalleconomy may `be increased without affecting the continuity or perfectionof the operation, insofar as the production of the desired end-effect isconcerned. Or, conversely, by changing such variable or variables in theWrong direction the overall economy of the operation may fall instead ofbeing increased. ln such case the direction of change of such variableshould of course be reversed so that the corrective effect will be toincrease rather than reduce the overall economy.

Usually the economy of an operation may be shown by a curve which bringsinto relation the economy overall produced by the operation as affectedby the change of one of the variables; for example, variation of thepitch of the propeller blades. Such a curve of economy will rise fromzero when the blades are set at zero pitch, reaching a maximum or peakeconomy value for a blade pitch 3,2Zl,759 Patented Dec. 7, 1965 Valuewhich will depend on various factors. Then, assuming such factorsthemselves remain unchanged, such curve will fall again at the pitch isincreased beyond such critical value of maximum economy or optimumoperation, the falling portion of the curve generally being concaveupwards over most of its falling portion, and reaching zero again for apitch of something less than ninety degrees. Such illustration ofvariation of the economy with variation of one variable is given by wayof illustration of one type of operation in which the curve of economyvs. change of a variable is of a form which includes a peak valuerepresenting maximum economy.

It is here noted that when the two variables (such as propeller speedand economy) are shown, the one along the horizontal axis of the graph,as abscissae, and the other vertically as ordinates, the curve ofeconomy will generally rise to the peak value and then fall, as thespeed is increased. Accordingly, the first derivative of such curve willchange between positive values and negative values at the peak of thecurve since the rate of change of the economy will, at such peak, becomezero, and, for speed values in excess of that corresponding to suchpeak, the rate of change will become negative, corresponding todecreasing economy values.

The economy of operation will be designated in terms of a unit whichdefines the kind of economy whose value is to be determined. Thus, forexample, in the case of a ship in free flight such economy mightproperly be defined in terms of miles per gallon of fuel consumed underthe flight conditions then existing; or, in some cases it might bedefined in terms of gallons per mile of iiight, depending on therelative values of the rate of gallons consumed compared to the rate offlight. For specified operating conditions affecting the ship at thetime of test, it is possible to produce or imagine a curve relatingoverall economy of operation in terms of gallons per mile as affected bya specified variable. Such variable may be propeller pitch, or propellerrotative speed. The overall economy existing at any given time will thenbe found as the ratio of speed divided by rate of fuel consumption, orthe inverse ratio, depending on which way the ratio is desired to bedetermined. Then, by making a change in the specified variable, anychange in the overall economy caused by such change will be reflected asa change of value of the ratio.

Briefly stated, it is a prime object of the present invention to providemeans to automatically effect changes in a selected variable so that,under the operating conditions then existing, other than such variable,the ratio of speed divided by rate of fuel consumption (as anillustration) shall be raised to the maximum possible value (namely, thepeak value). The correction operation shall then cease for the timebeing. Thus a maximum economy of operation will be assured when thecorrection is effected by change in the value or condition of theselected varia-ble, such change being in the proper direction toproduce, if possible, rise in the value of the determined ratio.

It is a further object of the invention to promptly detect by anautomatic operation or sensing operation, whether the selected variableis now being changed in direction to increase the economy; and in casethe direction of change of such selected variable is found to benegative (decreasing ratio), a reversal of the direction of change ofsuch selected variable will at once occur so that the correction willthen be produced in direction proper to effect increase in the value ofthe ratio, assuming that the peak value of the curve is greater than theratio then existing and determined.

It is a further prime object of the invention, once the correctivechange of such selected variable has been instituted, to effect changein the proper direction for increase of economy, to continue such changein such selected variable in such direction until a time arrives whenfurther change of such variable in that 'direction will actuallycommence to decrease the value of the ratio (the economy); in otherwords, to continue such proper corrective change until the peak of thecurve of economy has been attained (at which point the sign of the rstderivative, being the rate of change, changes between plus and minus orbetween positive and negative).v

It may also be stated that a prime object of the invention consists inthe provision of means to measure both of two rates whose ratio is to bedetermined, to divide one rate by the other to determine the ratiobetween them, and if that ratio is different from the ratio previouslyexisting between them, to deliver a signal to a corrective unit whichsignal will institute correction by an operation producted by a unitwhich units operation affects the value of one of the rates whose ratioinstituted the operation, such correction operation continuing until amaximum ratio value has been attained,

More specifically, it is a further object of the invention to providemeans whereby if the corrective operation instituted as stated in thepreceding paragraph is in the wrong direction, so that decrease of theratios value is produced by such corrective operation as instituted, areversal of direction of correction will promptly occur, thus ensuringcorrection in the proper direction for increase of the ratio due to suchcorrective operation, and with continuation of such corrective operationto the condition which produces a maximum ratio value as between the tworates in question.

Still more specifically, it is a further object of the invention toprovide a corrective servo-power unit, such as a motor, whose operationwill act to produce the correction operation of the corrective unit,such motor conveniently being reversible so that its corrective effectmay be produced in either direction as dictated by the needs of theoperation, and as explained in the preceding paragraph.

I have, by way of illustration only, previously referred to the controland operation of airplane propellers for maximum economy of operation byuse of the inventive features herein disclosed. It will be understoodthat these inventive features are also applicable to many otheroperations, and for many other purposes than the automatic control ofpropeller speeds and pitches for flight at preselected airplane speeds,under maximum economy conditions. Thus, for example, such units may beused for controlling the economy of production of power delivered by aprime mover driven generator, wherein it is desired to control theeconomy of the power production and delivery from such prime moverdriven generator unit. In the drawings hereinafter to be described,examples of such uses of the control units are disclosed. Other similaruses will suggest themselves to the student of this specification, and Ido not intend to limit the present invention to such particularlydisclosed uses and combinations, except as I may do so in the claims tofollow.

Other objects and uses of the invention will appear from a detaileddescription of the same, which consists in the features of constructionand combinations of parts hereinafter described and claimed.

In the drawings:

FIGURE l shows by way of illustration only, several typical performancecurves of an airplane equipped with propellers and shows how the economyof operation, overall, may vary under different operating conditions;these curves constituting a family of such performance or characteristiccurves;

FIGURE 2 shows by way of illustration only, a schematic layout of anEconometer Unit by which provision has been made for automaticallycomparing freeffight velocity with rate of fuel consumption, todetermine CFI the economy of operation, and for automaticallyreadjusting the power-motor speeds or blade pitches from time to time tomaintain these speeds or pitches at the values which will give maximumeconomy of operation; the scheme of FIGURE 2 being usable in connectionwith the proper elements of FIGURE 3, and also of FIG- URE 4, toestablish a complete layout for also automatically controlling andsynchronizing propeller blade pitches, and other functions;

FIGURE 3 shows schematically a control scheme for airplane control inwhich a free-flight velocity handle is provided to determine thepre-selected free-flight speed of the ship; this figure also showing theconnections from the units which are shown in the figure to the meterswhich meter the rate of fuel supply to the several power-motors andcomprise a portion of the synchronizing and controlling means;

FIGURE 4 shows schematically, an arrangement wherein the setting of thecontrol handle for free-night velocity serves to effect control andsynchronization of the pitches of the blades of the several propellersto maintain that desired free-Hight velocity; and this figure alsoindicates the connections from the units shown in this figure to themeters which meter the rate of fuel supply to the several power-motors,and comprise a portion of the synchronizing and controlling means;

FIGURE 5 shows a Flow Sheet of connections and operations correspondingto the layout of FIGURE 3; and

FIGURE 6 shows a Flow Sheet of connections and operations correspondingto the layout of FIGURE 4.

In FIGURES 3 and 4, to be hereinafter described, I have shown,schematically, means t0 generate and transform and deliver power toperform a function, and to control the economy of such powertransformation and delivery. Specifically, the power generating meansshown in the above figures comprises the propeller driving internalcombustion motors of an airplane, the transforming means comprises themeans to deliver the so-generated power to the propellers and thus toproduce traction, and the power delivering means comprises thepropellers which transform the power into the energy and dynamic motionof the airplane. The function is the end result in the form of thedesired speed of the airplane; and the means to control the economy ofsuch power transformation and delivery comprises the equipment disclosedin the present application, and its predecessors. Considered in reverseanalysis, the specific showings of FIGURES 3 and 4 include fuelconsuming prime mover units, means to control the rate of fuel input tosaid units, and means to transform and deliver the power from said primemover units and to perform the desired function at a determined rate ofdelivery, namely the means to transform the delivered power to adetermined speed of the ship. The means to control the economy of thepower transformation and delivery comprises the novel ratio determiningelement shown in FIGURE 2, together with the servo-motor or equivalentelement, whereby changes in the determined ratio are properlycommunicated to the servo-motor in the. proper direction of drive ofsuch motor, and for the purpose of effecting corrections in the overalloperation which,v shall ensure rise of the economy of operation to the.peak value possible under the operational conditions then existing.

Thus, in both of FIGURES 3 and 4 a prime-mover is` provided, driving apropeller, with throttle and pitch control available to enableproduction of the desired rate of delivery of the power needed to propelthe ship at a predetermined speed; and with the presence of the abilityto effect such speed of drive by various combinations of throttlecontrol, pitch control, and propeller speed. Thus the illustration oftwo forms of propeller driven ship is by way of illustration ofembodiments which include the overall combinations of elements which acttogether to enable production of that intended end result (speed of sule) the ship) with consumption of a minimum nate of the fuel per unittravel; which is the same as producing a desired rate of power outputwith a minimum rate of fuel input. Accordingly, the illustration of mypresent invention in connection with an airplane drive control is not byway 'of any limitation of the usefulness of the invention, except as Imay limit myself in the claims to follow. With the foregoing briefstatement of relationships, the following description is in order:

Fior any given set of openating conditions, such as power demand, etc.,there is an optimum set of specifications in the operation of thepropeller to secure maximum economy of operation. For example, for anyspecified propeller the economy of operation thereof will vary withrotational speed, and such variation may be determined for a given pitchof the blades, etc. For any such given set of conditions, however, acurve plotted to represent ovenall economy vs. rotational speed willrise to a maximum value, and will then descend, so that there is, forsuch propeller and for any specified pitch angle of the propellerblades, an optimum speed of rotation to secure maximum economy in -itsconversion of fuel into power to sustain flight. A family of curves maybe plotted showing overall economy vs. rotational speed, each curveshowing overall economy for a specied blade pitch, all other openatingconditions remaining constant. Other families of curves may also bedetermi-ned and plotted between overall economy and single selectedvariable operating conditions. For example, such a family of curves maybe plotted wherein each curve shows overall economy vs. blade pitch,each such curve showing overall economy for a specified rotative speed,all other operating conditions remaining constant. An innite number ofsuch curves may be plotted, each showing the variation of economy with aselected variable condition, all other conditions being held constant.Such other variables may include height above sea-level, airtemperature, relative humidity, conditions such as icing, etc. It is,however, desirahle to always operate the several power motors at suchconditions of rotative speed, pitch of blades, etc., as will givemaximum economy of operation overall. This is merely another way ofsaying that it is desirable, once we have determined on a velocity offree-night, to maintain that velocity with the power-motors andpropellers operating under those conditions which fwill require theleast total fuel for the trip. I shall now show how I have providedautomatic controls which will give these results.

For this purpose reference may be had to FIGURE 2 which showsschematically a set of controls largely supplemental to those shown inFIGURE 3, presently to be described, and other arrangements such asshown herein, and in Letters Patent, No. 2,794,507, issued June 4, 1957,from which case the present application is descended. FIGURE 3 has notbeen reproduced in FIGURE 2 largely to simplify these disclosures. InFIGURE 2, I have reproduced the generator 492 whose rate of rotation isproportional to the velocity of free-flight, and the generator 545 whoserate of rotation is proportional to the rate of fuel consumption. Thelines Silla and Sfida leading from these generators are also shown inFIGURE 2. These lines carry frequencies proportional to air speed andrate of fuel speed, respectively. In FIGURE 2, I have shown means toautomatically compare these frequencies and determine at all times theratio between them. This means as shown in FIGURE 2 comprises twocylindrical members 555 and 565, mounted for rotation on theirlongitudinal axes, and parallel to each other. The element 565 isprovided with the surface groove 567 which is of logarithmic form, landthe element 565 is provided with the surface groove 56S which is also oflogarithmic form. These grooves are conveniently determined lon thenaperian system, and each groove includes at its beginning or left-handend a turn which is arbitrarily formed merely to take care of theinnitely long 6 portion which such curve 'would otherwise have, andwhich arrangement is proper in view of the uses to which these groovesare to be placed, as will presently appear.

Furthermore, these two grooves are conveniently cut for severalrevolutions around each cylinder, so that a `sufficiently largenumerical denomination range of absolute values may be accommodated on acylinder of convenient length. For example, if the free-flightvelocities to be taken care of run as high as 600 miles per hour, thegroove of the cylinder S65 should be so cut as to read to that amount,or proportionate thereto; and if the rate of fuel consumption shouldamount to as much as 1000 gallons per hour the groove of the cylinder566 should be so cut as to read to that amount, or proportionatethereto.

The cylinder 565 is mounted for rotation, but not for endwise movement;whereas the cylinder 566 is mounted for both rotation and endwisemovement. That fact is attested by the dotted portions at the ends ofthe cylinder 566 representing, at the left-hand end, the normal orinitial or u-nmoved position of such cylinder, and at the right-handend, the fully moved yor extreme position of such cylinder. Betweenthese two cylinders is movably mounted or carried the slide 569. Thisslide preferably has its side Walls formed on arcuate segments to snuglyembrace the surfaces of the two cylinders, but the slide is free to movereadily according to the dictates of the grooves. This slide has twooutwardly extending pins which engage the grooves of the two cylinders,so that the slide will function according to the respective cylinderpositions and conditions of cylinder rotation. Furthermore, it will beevident that the endwise moved position of the slide will depend on thenumber of turns which the cylinder 565 has performed from its initial orunm'oved position, the slide moving toward the right in FIGURE 2 as thecylinder 565 rotates in the direction representing increase of velocityof free-flight. The slide also engages the groove of the cylinder 566.Therefore the endwise position of such cylinder 566 with respect to theslide will depend on the amount by which said cylinder has been rotatedfrom its zero position against the force of the spring 578. That amountof rotation against such spring will depend on the rate of fuel feed.Such rotated position of the cylinder 566 will cause endwise movement ofsuch cylinder towards the left in FIGURE 2. Thus the net e-ndwisemovement of the cylinder 566 from its zero or starting position (shownby the dashed lines in FIGURE 2) will be equal to the rightward movementof the slide (produced Aby the rotated position of the cylinder 56S)minus the leftward movement of the cylinder 566 with respect to thesli-de (produced by the rotated amount of the cylinder 566). In thisconnection it will be understood that the two cylinders 565 and 566 arerespectively turned, in comparison to the manner in which their groovesare formed, in such directions that the velocity cylinder 565 tends toset the slide towards the right, whereas the turning of the fuel rate ofow cylinder 566 acts to move said cylinder 566 back towards the left dueto engagement of a pin of the slide with the groove of such cylinder566. It is here noted that provision is made to turn each cylinderthrough a total angular displacement from its zero position tocorrespond to the flight speed or to the rate of fuel flow as the casemay be represented by such cylinders turned position. This will befurther explained hereinafter,

Another way of considering the matter is that the slide tends at alltimes to subtract the reading of the cylinder 566 as would be shown byits turned position, from the reading of the cylinder 565 as would beshown by its turned position. Due to the simultaneous engagement of theslide with both cylinder grooves, and the fact that the cylinder 565 isheld against endwise movement whereas the cylinder 566 is capable ofendwise movement it follows that the cylinder 566 will assume an endwisemoved position which is equal to the difference of axial cornponents ofthe turned positions of the two grooves; in

other words the cylinder :56 will always assume an endwise movedposition which is the difference between the logarithm of the velocityof free flight minus the logarithm of the rate of fuel consumption. Thisdifference of logarithms is the logarithm of the quotient obtained bydividing the rate of free-flight by rate of fuel consumption, or milesper gallon or per hundred gallons, or the like. The endwise movedposition of the cylinder 566 may be readily indicated by the circulargroove 559t1 near one end of such cylinder, and the suitable indicatoris readily engaged with such groove to read on a scale of miles pergallon, or the like. In the present case I make use of the endwisemovement of this cylinder 556 to actuate certain throttle, rotationalspeed, and pitch controls which will automatically re-set at all timesthe various operational elements to the optimum conditions to which Ihave referred.

At this point I will mention that it is of course needed to insure thatthe cylinders 566 and 565 will at all times assume turned conditionsproportionate to the rates of fuel consumption and of flight,respectively, and also to ensure that the turned position of eachcylinder shall remain unchanged until there is a change of the value ofthe corresponding function. Such changes of corresponding function arechange of the turned position of the cylinder 555 with change of fiightspeed, and change of the turned position of the cylinder 556 with changeof rate of fuel feed or change of power. I shall now show one meanswhich I use to accomplish this result:

I provide a small induction motor element 570 for the cylinder 565 andanother small induction motor element 57i for the cylinder 556. Each ofthese induction motor elements includes the polyphase Wound stator 572and the rotor element 573 or 574, as the case may be, infiuenced by itsstator element. The rotor 573 is connected to the shaft 575 of thecylinder S455, and the rotor 574 is connected to a shaft 576 which issplined to the cylinder 565 so that the turned condition of the cylinder566 is at all times dictated by the rotor 574 even while allowing forendwise movement of said cylinder 556. The springs 577 and 57S tend toreturn the shafts 575 and 576 and the corresponding cylinders 555 and566 respectively, to their initial or zero positions; and these springsare calibrated so that they permit turning of the respective cylindersby amounts proportionate to the respective rates to be measured. In thisconnection it is noted that the torques developed by the respectiverotors 57? and 571 will be proportionate to the frequencies of polyphasecurrents delivered to their stators, so that the turning efforts exertedby the respective rotor shafts will result in turnings of said shaftsagainst their springs until these turning efforts have been equalized bysaid springs, so that the turned positions of the cylinders will at alltimes be proportionate to the frequencies heretofore referred to.Manifestly any other suitable means might be substituted for convertingfrequencies of the lines 541ia and Sfida into proportionate angle ofturn if desired without departing from the spirit of the presentinvention. For example, there might be used centrifugal devices operatedat the speed of the motors driven by the frequencies on the lines Sillaand 546@ to set the cylinders to turned positions corresponding to saidfrequencies, or other schemes might be substituted for that indicated inFIGURE 2.

As respects the induction units 57@ and 571i, it will be understood thatthe torque delivered by the squirrel cage rotors S73 and 574 of theseunits will depend also on the voltage developed by the units 492 and545, so it will be desirable that means be provided for maintainingconstant voltages delivered by these generators at varying speeds, asmay be done for example by regulation of their field strengths, somewhataccording to the disclosures of Letters Patent No. 2,612,956, previouslyreferred to herein and issued to me, and as shown for example in FIGUREl of that patent at 135. Also, wound rotors CII might be used in theinduction units 57@ and 571, with suitable means to adjust theresistances in series therewith to thereby ensure desired calibration ofsaid units with respect to the springs 577 and 578. It is of courseunderstood that the rotors serve to turn the respective cylinders torotated positions corresponding to the respective frequencies, and thenthe rotors remain stationary so that the conditions of torque becomethose of an induction motor at slip. In FIGURE 2, I have indicated thereversible motor 557 corresponding to the reversible motor 557 in FIGURE3. Such a motor 557 is also shown in FIGURE 4. This motor in FIGURE 2Serves to control the rheostat 561 which controls the frequency ofpolyphase current supplied over the lines 539 (FIGURE 3) to thepropeller pitch control devices, so by control of this motor 557 inFIGURE 3 we shall control motor speed of the power-motors and propellersby pitch control, while maintaining the rotating speeds of thepower-motorpropeller units in synchronism. These controls are effectedby the endwise positioning of the cylinder 565 of the Econometer shownin FIGURE 2, as I shall now show.

Reference to FIGURE l shows typical performance curves for a specifiedpropeller, as respects variation of overall efficiency or economy withrotational speed, for several typical conditions of blade pitch,elevation above sea-level, etc. Each of these curves shows the aboverelationship between overall efficiency or economy and rotativepropeller speed for such stated conditions and other conditions.Evidently an infinite number of such curves might be plotted, each oneon the basis of a change of specified amount in any one of theconditions affecting economy. Other similar curves could be plottedshowing the relationship between overall efficiency or economy and bladepitch or angle of attack for a given set of conditions includingrotative speed, elevation above sea-level, humidity of the atmosphere,icing, and many other factors. In such case, too, an infinite number ofsuch curves might be plotted, each on the basis of a change of aspecified amount in any one of the conditions affecting economy. Thusthe full line curve 579 may represent such performance curve for a givenset of conditions, and curves 58u, 581 and 582 may represent performancecurves under three other sets of conditions. Now it will be noted thatin the case of each curve there is an optimum point, indicated by thepeak of the curve, these peaks being shown at 533, 584., 535 and 585 forthe four curves 579, 580, 581, and S82, respectively. The attainment ofthe maximum overall efficiency or economy may be effected by change ofeither blade pitch or rotational speed, or both, as will hereinafterappear. When the control for maximum economy is effected by change ofrotative speed it is desired that no matter what operating conditionsmay be in force, the rotational speed of the power motors shall bebrought to that value which will correspond to the peak of the curve forsuch operating conditions, so that the velocity of free-Hight may bemaintained at minimum expenditure of fuel, and for other desirablereasons which will be evident.

When the control for maximum economy is effected by change of bladepitch it is also desired that no matter what operating conditions may bein force, the blade pitch of the propellers shall be brought to thatvalue which will correspond to the peak of the curve for such operatingconditions, so that the velocity of free-flight may be maintained withminimum expenditure of fuel, and for other desirable reasons which willbe evident. When the control is by variation of rotative speed it isevident that provision must be made for automatically bringing the bladepitches of the propellers to proper values for development of the totaltraction needed to maintain free-fiight speed of the airplane at thespeed pre-set by the pilots control unit such as the handle 428 inFIGURES 3 and 4. When the control is by variation of blade pitch it isevident that provision must be made for automatically bringing therotative speeds of the motors and propellers to proper values fordevelopment of the total traction needed to maintain the freeiiightspeed of the airplane at the speed pre-set by the pilots control unitsuch as the handle 428 above mentioned. All such means are hereindisclosed.

Now examination of these several curves (FIGURE 1) shows that in passingfrom one of them to another we may find it necessary to increasepower-motor speed, or in other cases to reduce such speed, to operate onthe peak of the curve which corresponds to the new operating conditions.Thus, if operating or other conditions change so that we may pass fromthe curve 579 (peak at 1575 rpm.) to the curve 582 (peak at 1875 r.p.m.)We should increase the r.p.m from 1575 to 1875; Whereas if operatingconditions change so that we pass from the curve 579 to the curve 581(peak at 1325 rpm.) we should decrease r.p.m. from 1575 to 1325. It isalso noted that in passing from the optimum condition of one curve (dueto one set of conditions) to the optimum condition of another curve (dueto another set of conditions) we may find that our new overall economyis either greater or less than that previously existing. This is thesame as saying, for example, that the best performance possible at oneelevation above sea-level will be different from that possible at someother elevation above sea-level. It is thus evident that we shall, inorder to hold the optimum economy at the new set of conditions bycontrol of rotative speed, sometimes have to increase such rotativespeed,` and sometimes decrease such speed by proper control of the motorgenerator unit 433; and it is further evident that the movements of thecylinder 566 of the Econometer will sometimes be to the right in FIGURE2, and sometimes to the left in said figure, depending on whether or notthe new set of conditions give greater or smaller optimum economy. It isfurther evident that it is desirable to bring about the controls of therheostat 561, and therefore of the operations and direction of rotationof the motor 557, in FIG- URE 2, entirely automatically, and merely bymovements of the cylinder 566 endwise as the economy of operationchanges from time to time, due to changing conditions of operation. Atthe same time it is an object to ensure that in every case there-adjustments of the rheostat 561 will be such as to ensure optimumconditions of economy under the new conditions of operation. In otherwords, it is the object to ensure maximum economy of operation, and-minimum fuel consumption at all times, automatically produced by thecontrols now to be disclosed.

Referring to FIGURE 2 I provide a linger 587 which engages theencircling groove 569a of the cylinder 566 so that said finger movesback and forth as dictated by the changing economy of operation.Movements of said finger towards the right represents increase ofeconomy, and movement towards the left, decrease of economy. Said fingercarries a motor circuit closing contact element or finger 538, and amotor contactor 589 is actuated back and forth by this finger 585i butwith a slight amount of play, due to the pin and slot engagement shownat 59d. Said contactor 589 has contacts facing in both directions. Thereis a contact follower 591 which is mounted to ride back and forth withthe finger 538, being moved in either direction by the contactengagements, and said contact follower 591 carries the two contacts 592and 593 which are insulated from each other, and are separated slightlymore than the total separation between the two contacts of the motorcontactor 589. In the position shown both of the contacts of the motorcontactor 589 are disengaged from the contacts 592 and 593 of thecontact follower 591.

The contact follower 591 has the two contacts 592 and 593 so mountedthat as the motor contactor moves in either direction and contact isestablished with either of the contacts 592 or 593, further movement ofthe motor contactor will cause said contact follower to follow themovement of the motor contactor to some new position of measured economyas established by the changed conditions of operation due to suchmovement of the motor contactor, so that in case of slight retrogrademovement of the motor contactor at such new position the contacts ofsaid motor contactor will both disengage from the respective contacts592 and 593, allowing the contact follower to remain in its new positionfor the time being, but ready for another movement in either directionas needed at some future time.

Just behind the contact 592 is another contact 594 also carried' by thecontact follower 591, and normally free of the contact 592; and when themotor contactor 589 is moved towards the left (decreasing economy) itrst engages the contact 592, and then if movement towards the left iscontinued slightly, there will be established engagement with thefurther contact 594 for reasons presently to become apparent. Thearrangement is such that in movement towards the left (lowering economy)the movement of the motor contactor 589 will not cause the contactfollower to actually commence movement towards the left merely byengagement with the contact 592 but there must be a further slightleftward movement, to bring the contact 592 against the contact 594 inorder to cause leftwardv movement of the contact follower S91.

The contact follower 591 also carries another contact 595 which will beengaged by the contact 596 of the motor contactor 589, slightly prior toengagement of the contact 592 by the adjacent contact of the motorcontactor 589. In other words, during a leftward movement of the finger587 (lowering economy) the sequence of contacts is as follows: motorcontactor with contact 595, then motor contactor with contact 592, thencontact 592 (and motor contactor) with contact 594, both of contacts 595and 592 remaining engaged.

The rheostat shifting motor 557 is shown as having the two field coils558 and 559 of opposite windings so that either of these coils may bebrought into the series circuit with t-he motor armature, but withreversal of direction of armature rotation. It is intended that when aslight movement of the finger 587 of the economy ratio determiningdevice takes place in either direction, there shall be set up a sequenceof operations to reset the motor 557 and therefore the rheostat 561 tobring about a new speed of the motor generator supplying the lines 539so that the new speed of power-motor operation shall ensue. Such slightmovement of the finger 587 in either direction also moves the motorcontactor; and in case of movement towards the right the contact 593will be engaged after a very slight movement of the motor contactor,whereas in case of movement towards the left the contact 595 will befirst engaged and very shortly thereafter the contact 592 will beengaged. The motor contactor 589 connects by the line 597 with a sourceof direct current supply, such as the battery 598 (or battery shown inFIGURE 3), so that one pole is always in connection with said motorcontactor 589. The contact 593 connects to the armature side of theseries motor 557 by the line 599, and the solenoid of a relay 600 isplaced in this line, so that said relay is always energized when thecontact S93 is engaged. The contact 592 connects by the line 601 withthe line 599 at a point beyond the solenoid 600, and the solenoid of asecond relay 602 is placed in this line 601.

It is now evident that whenever either of the contacts 593 or 592 isengaged by the motor contactor one pole of the supply line will beconnected directly to the armature side of the motor S57. There isprovided a reverser 603 including the solenoid 604 acting on thearmature 6% to pull same down against the spring 696, and said armaturecarries the flexible projection 607 at its lower end. The Contactcarrier 608 is pivoted at 609, and has the arm 61d carrying the Contact611. There are placed two contacts 612 and 613 adjacent to one extrememovement of the contact 6M, and two contacts 6M and 65 adjacent to theother extreme of movement of said contact 611. In either extreme ofmovement of the reverser the contact 611 will engage one of these pairs,62-6i3 or 614-615, as the case may be. The arm 61@ has the cam surfaceor block 616 which will -be engaged on one or the other of its faces bythe ilexible projection 667, so that said arm will be tilted rst in onedirection and then in the other with succeeding excitations of thesolenoid 661i. In other words, the single solenoid serves to operate thereverser by successive pulses to the solenoid, first in one directionand then in the other direction, to place the contact 611 first inengagement with the contacts 612 and 613, and then in engagement withthe contacts 614 and 61S.

The free terminals of the two eld coils 558 and 559 connect to thecontacts 6M and 613, respectively. The reverser contact 62 connects tothe other terminal of the battery or source of current by the line 617,a ilexible connection 618 being provided in this line if desired. It isnow evident that movement of the motor contactor 589 in either directiondue to change in measured economy as determined by the movement of thecylinder S66 end- Wise will result in closing of a circuit through themotor 557, and that rotation of such motor will be in directiondependent on the position of the contact 611 and arm 616 as last set bya previous operation. Such direction of motor operation may, thereforebe to either increase or decrease rotational rate of the power-motors ofthe airplane, and up to this point the control device has merely servedto bring the motor into operation for a corrective result. If thedirection of motor rotation be such as will establish conditionsresulting in increased economy, then there will promptly follow amovement of the cylinder 566 towards the right in FIGURE 2, whereas ifthe direction of motor rotation be such as will establish conditionsresulting in a decreased economy, then the cylinder 566 will promptlycommence to move towards the left in FIG- URE 2. It has already beenshown that sometimes changed conditions will require increased rotativespeed of the power-motors to ensure optimum economy, whereas in othercases a decrease of rotational speed of the power-motors will berequired; but with the arrangement so far disclosed the closing of themotor circuit may or may not be for motor operation in the properdirection. I shall now show how such proper direction of motor rotation(motor 557) will be automatically produced:

Itis to be remembered that when once an optimum condition of operationhas been produced, power-motor speeds being proper for such optimumcondition, the motor contactor 589 stands free of all the contacts 522,593 and S95, and until there comes a change in the economy as metered bythe position of the cylinder 566 this condition will continue. As soon,however, as there is any change of operating conditions which willchange the economy, the cylinder 566 will shift either to the right orto the left, thereby establishing connection to one or the other of saidcontacts, and setting into motion the corrective devices hereindisclosed. Such corrective action should and will then continue in theproper direction until the motorpropeller condition (rotational) of thepower motors has been brought to the point for optimum economy under thenew conditions, whereupon further correction will cease. This result isobtained as follows:

First assume the condition that a slight increase of economy occurs sothat the cylinder S66 is moved towards the right. In such case the motorcontactor 589 will shift towards the right and almost immediatelycontact will be established with the contact 593. This will close themotor circuit for motor rotation .in direction dictated by the previoussetting of the reverser. If that direction is correct for the newoperating conditions, that is, if the new operating conditions are suchthat maximum economy of operation will be secured by increase ofpower-motor rotative speed, then the action of the cylinder movementwill be cumulative, and it will continue to move towards the right, aswe are improving economy of overall operation by increasing thepower-motor speed. This might be the case for example if the nightconditions changed so that instead of the curve 579 of FIGURE 1,representing the relation of overall economy to rotative speed, thecurve 532 of said figure has now become the one representing therelation of overall economy to rotative speed. Presently we shall arriveat a power-motor speed of 1875 r.p.m. such that further increase thereofwill cease to improve economy, being the peak point 586. Finally, as wemove over the peak of the curve the overall economy will actuallydecrease. At that instant, when we have just passed the peak of thecurve, there will occur a retrograde movement of the finger 587, and ofthe motor contactor S8?, so that at once the motor contactor will breakaway from the contact 593, opening the motor circuit, and leaving thepower-motors to continue operation at the newly adjusted rotationalspeed, and with maximum economy under the operational conditions now inforce.

Next suppose that when the motor contactor 589 moves to the right andengages the contact 593, thereby closing the motor circuit, thedirection of motor rotation will be found to be such as to bring aboutan actual decrease of economy. This condition might arise for example incase of transition from the curve 579 to the curve 531 (FIGURE l).Examination of FIGURE 1 shows that the rotational speed of thepower-motors should now be reduced to secure peak curve economy underthese new conditions of operation. It is remembered that the reverserwas previously set to position to cause rotation of the motor 557 indirection for increase of power-motor rotational speed. Such being thecase (reverser being in its previously set position), we have commencedmotor rotation in the wrong direction, and the cylinder 566 willcommence to move towards the left, caused by lowering economy ofoperation. It is thus evident that provision should be made for shift ofthe reverser position so that the motor 557 will be caused to rotate indirection to reduce power-motor rotational speed. This is done asfollows:

It was previously stated that there is a .pin and slot connection at thepoint 599 between the finger 588 and the motor contactor 589, so aftercontact has been established between the motor contactor 589 and thecontact 593, such engagement of contacts will be retained, notwithstanding a slight backward or leftward movement of the nger 587,until the contact 596 engages the contact 595. Said contact 595 connectsby a line 619 to a contact 620 of the relay 621. Said relay has itssolenoid 622 connected at one end to the line 623 which extends to acontact 624 of the relay 600 whose solenoid is in the motor circuit fromthe contact 593 as already explained. The armature contact 625 of therelay 600 connects by the line 626 to the ybattery terminal to which themotor contactor connects, so that when the contact 593 is engaged by themotor contactor to place current through the motor, the relay 660 raisesits armature, and the contact 624 is engaged by the armature contact625, and the solenoid 622 of the relay 621 is thus connected to one endof the source of current. The other end of the solenoid 622 connects bythe line 627 to the contacts 612 and 615 of the reverser, so that ineither position of said reverser said line 627 connects back to theother terminal of the source of eurent. It is now evident thatregardless of the position of the reverser at the commencement of theseries of operations, as long as the motor contactor 589 retainsengagement with the contact 593, even during the slight backwardmovement to engage the contact 596 against the contact 595, the solenoid608 is energized, and thus the solenoid 622 is also energized to retainits armature elevated. Said armature carries the contact 628 which ismounted on a block of insulating material; and said contact 623 connectsby the line '13 629 to one end of the reverser solenoid 664, the otherend of said solenoid connecting by the line 630 to the line 617, leadingback to the source of current.

The line 623 which connects to one end of the solenoid 622 of the relay621 also connects to the contact 631 in position to be engaged by thearmature of said relay, which armature connects by the line 632 to theother terminal of the source of current. Following out the conditions sofar established it will be seen that the engagement of the motorcontactor 569 with the contact 593 served to raise the relay 661i, whileat the same time bringing the motor into operation in the wrongdirection. The raising of the relay 660 served to energize the relay621, raising its armature, thus causing engagement of said armature withthe contact 631. This will establish a 4circuit from the battery 598,over the lines 626 and 632 to the armature of the solenoid` 622, thenceIby contact 631 to top end of solenoid 622, through said solenoid, overline 627 to reverser contacts 612 and 615, to contact 611 (when thereverser is in one of its extreme positions or the other), pigtail 618,and over the line 617 back to the battery. Thus it will be seen thatonce the armature of the relay 621 has been raised (the reverse being ineither extreme plosition of its movement) a local circuit is establishedthrough the contact 631 which will hold the armature of the relay 621 inraised position even when the armature of relay 600 is deenergized bymovement of the motor contactor 589 to the left so as to disengage fromthe contact 593. Thus the relay 621 is now self-energized by a holdingoperation. Raising of said armature of relay 621 served to close circuitthrough the reverser solenoid, thereby delivering an impulse andreversing the contacts and also reversing the lield of the motor 557which is the desired result. At the same time it will be noticed that asthe contact 611 of the reverser was thrown from one extreme of movementto the other it momentarily opened the circuit of the line 627, so thatthe solenoid 622 of the relay 621 was momentarily de-energized anddropped its armature to the position shown in FIGURE 2 thus terminatingthe self-energization of such relay 621. However, as soon as thereverser contact 611 reached the other extreme of movement itre-established contact with the other of the contacts 612 or 615, as thecase may be, ready for another operation at a future time. The lockingContact 631 and the temporary holding of the relay 621 serves to ensurethat the above operation will be carried through even in case of actualopening of the circuit between the motor contacter 539 and the Contact593 prior to closing of the contact between the motor contacter 589 andthe contact 595.

Upon causing reversal of the reverser as just explained the motor 557will reverse rotation and thus cause the power-motor rotational speed tobe modied in the proper manner to bring about increased economy, thuscausing the cylinder 566 to again move towards the right, and bringinginto action the contact 593. During this operation the motor contacterwill shift to engagement with the contact 593, then leave the contact592, and supply of current to the motor 557 will come from said contact593 until the rotational speed of the powermotors has been increased tothe value needed to attain the .peak of the curve of overall economy nowavailable. When the new condition of maximum economy has been reachedand the peak of the curve is slightly over-run, retrograde movement ofthe iinger 587 to a very slight degree will open the circuit by backingthe contactor 589 away from the contact 593 and bring the correctiveoperation to termination. Thus we have effected correct re-adjustment ofthe power-motor speed in both of the cases where the initial movement ofthe cylinder 566 is towards the right, meaning that in the initialdisturbance there was a tendency towards increase of economy asindicated by operation of the Econometer- I shall now consider theconditions where the initial condition of disturbance is such that thecylinder initially moves towards the left, that is, towards lowereconomy conditions.

Assume that the original disturbance was such as to decrease economy,thereby moving the cylinder 566 and motor contactor towards the left.Slight movement will bring the contact 596 into engagement with thecontact 595 thereby delivering an impulse over the line 619 to thecontact 626; and since the relay 621 was locked up from a previousoperation, this impulse will continue through the contact 628 and line629 to the reverser solenoid, thereby setting the reverser over to itsopposite position. Slight further movement of the motor contactortowards the left will bring the motor contactor 589 against the contact592. This will supply current to the motor over the line 601 andsolenoid of the relay 602, and line 599; and if direction of the motoroperation was correct (after having been just re: versed by thereverser) for increase of economy, then` motor operation in the properdirection will commence for increase of economy. Now, since the relay600 is down, its armature 625 will engage then contact 633, whichconnects lby the line 634 with the contact 635 above the armature 636 ofthe relay 602, so that' when the relay 662 raises its armature it willbe locked up, and current will continue to be supplied to the motorirrespective of the continued engagement of the motor contacter 589 withthe contact 592. Therefore the increase of power-motor overall economywill cause the cylinder 566 and nger 587 to move to the right, breakingcontact between the motor contactor 589 and the contact 592; but still-current `for corrective action will be supplied to the motor due to thelocking up of the contact 636 against the contact 635. This correctiveaction to increase economy will continue until finally the contactor 589moves over far enough to engage the contact 593, whereupon current willbe supplied through the relay 601i in manner already explained. `Theenergizing of the relay 660 will cause its armature to rise therebyopening the circuit over the line 634; and since the line 601 is nolonger supplying current through the relay 602 said relay will fall andopen the circuit at the contact 635. Thereafter current for continuedcorrective operation of the motor will be supplied over the line 599from the contact 593, and when the condition of optimum or maximumeconomy is reached the motor circuit will open at the position of thecontact 593, due to reversal of cylinder movement, and the operation hasbeen completed.

Next we consider the condition encountered when the disturbance tooperating conditions causes movement of the cylinder towards the left,and in which the reverser is set for motor operation in such directionas to continue such left-hand movement of the cylinder by motoroperation to still further reduce the economy. For example, assume thatwhen the motor contacter contact 596 has engaged the contact 595 thereverser has thrown the contact 611 to position to cause operation ofthe motor 557 in the economy reducing direction. In such case the linger587 will continue to move towards the left, after engagement of thecontacts 596 and 595, and almost immediately thereafter the motorcontacter 589 will engage the Contact 592, causing motor operation inthe wrong direction, and the linger 587 will continue its movementslightly towards the left, bringing about engagement of the contact 592with the contact 594-. Immediately there will be delivered an impulse ofcurrent to the solenoid 604 of the reverser, and at once the reverserwill throw over, reversing the fields of the motor, and reversingdirection of motor operation. This will immediately cause a correctiveaction to take place in the proper direction, and the economy ofoperation will rise, with attendant movement of the finger 537 and motorcontacter towards the right. During these operations the relay 600 wasnot yet energized and its armature was down, but the relay 602 wasenergized by engagement of the motor contacter with the contact 592, sothat said relay 602 will be raised and locked up until the motorcontactor engages the contact ?3. This will energize the relay 600 whichwill then rise opening the holding circuit at the point 633, and currentwill continue to be delivered to the motor in proper manner to continuethe corrective effect until the peak of the performance curve is reachedwhereupon very shortly thereafter the slight backward movement of thefinger 587 and motor contactor 589 will open the circuit, the operationhaving been completed.

Consider the controls of FIGURE 2 in conjunction with those of FIGURE 3,and on the assumption that the lines 553 and 564 of FIGURE 3 have beendiscarded and the upper armature terminal of the motor 559 in FIGURE 3is connected to the line 599 in FIGURE 2, and that the two fields of themotor 599 are connected to the reverser contacts 613 and 614 of FIGURE2, so that the motor 557 of FIGURE 3 becomes in effect the motor 559 ofFIGURE 2 and is controlled by the Econometer according to the principlesalready set forth in detail. Then it will be seen that a very completeand fully automatic control system will be provided. If we assume thatthe original setting of the handle 437 for power-motor speed control wasbelow the normal speed range required for the pre-set free-fiightvelocity as dictated by the setting of the handle 428 it will be seenthat the only control required to be manually made during iiight will bethat of the air-speed as determined by the handle 428. When that handleis set to a given velocity condition the power requirements needed tomaintain that velocity will be automatically adjusted from time to timeby the motor 549; the power-rotational speeds will be automaticallyadjusted from time to time to maintain maximum economy of operation,that is, lowest fuel consumption consistent with the free-flightvelocity being maintained; and the propeller blade pitch settings willbe automatically adjusted from time to time to ensure the consumption ofthe power being delivered by the power-motors and as determined by therequirements of the free-flight velocity; and furthermore, allpower-motors will be required to deliver the same amount of power(synchronized for power); and all power-motors will be synchronized forrotational speed. Whenever the pilot may re-set the handle 428 to a newfree-flight velocity the power setting will automatically be reset, thepower-motor rotational speeds will adjust themselves for maximum economyof operation under these new conditions; and all other factors will alsobe re-set to meet the new conditions, all without additionalmanipulation or thought on the part of the pilot, and while maintainingsynchronism of powers and rotational speeds of all of the power-motors.Thus the pilot need concern himself only with the one control handle orelement during flight. At the same time he will have knowledge that thedesired velocity is being maintained, and the trip being accomplishedwith minimum amount of fuel consumption, consistent with that velocityand the existing conditions such as elevation above sea-level, etc.

I shall hereinafter describe FIGURES 3 and 4 in sufficient detail tomake clear the airplane control arrangements shown in those figures, sothat the statements `contained in the foregoing paragraph will be betterunderstood, and the means whereby the results stated in that paragraphmay be produced.

It is noted that in the schematic layout of FIGURE 2 the frequencydelivered over the lines from the generator 545 to the induction unit571i is the control frequency by which the several power-motors arebeing controlled for power output, and by which said power-motors arebeing synchronized. Therefore this frequency from this gen- I5 erator545 will be proportional to the power out-puts and rates of fuel tiow tothe several power-motors. If desired, however, a special fuel meteringdevice or meter might be placed in the fuel line delivering fuel to thepower-motors, and driving a polyphase generator, which generator wouldbe the one delivering the frequency to tne lines leading to theinduction unit 571. In such case the generator 545 might be a specialgenerator driven by a special fuel metering device by which the fuelactually delivered to the power-motors was measured, and thereby a veryaccurate and positive measurement of fuel consumption would be ensuredfor operation of the ratio determining device.

If desired a double-throw, three pole switch might be provided for thesmall motor 557, so that thereby said motor could be connected either-as shown in FIGURE 3, or as shown in FIGURE 2, at the option of thepilot. I have not deemed it necessary to illustrate all of the-connections for such alternative arrangement, and for such switch, asthey are more or less self-evident.

It is noted that the corrective effect of the scheme of FIGURE 2 t0ensure optimum economy conditions of operation, is due to closure of acircuit for operation of the motor 557 whereby the corrective operationis directly performed. That closing of the circuit, with the disclosuresso far described, depends on a change of position or economy reading ofthe finger 587 due to change of the cylinders 565 and 566, or one orboth of them. Until such a change of the position of this finger 587takes place the corrective effect will not be instituted. Generally achange of operating conditions will of itself directly result in changeof economy or operation, as determined by these cylinders 565 and 566,as will be evident by comparison of the various curves 579, 580, 531 and582 of FIGURE 1. A change from or between any of these curves, at agiven propeller r.p.m. will result in a direct change of economy (asevidenced by the different elevations of these curves at a givenr.p.m.), so it will usually happen that a change of operating conditionswhich results in operation on a new curve of Net Overall Efficiency willof itself result in setting into motion the corrective operation of theeconometer of FIGURE 2.

Sometimes there will occur changes of operating conditions which, whilecausing operation thereafter to be on `another curve of net overallefficiency, still will not cause at once institution of the correctivechanges, or effects. Thus, if for example the new curve passes throughthe point of the curve on which operation has previously been occurring(usually the peak of such curve), there will occur no change of economyat the r.p.m. at which the power-motors have been operating, andtherefore no corrective effect will be produced by Ithe Econometerbecause the position of the finger 587 will not thereby be shifted toinstitute such corrective action. For example, if we have been operatingat the point 583 of FIGURE l (being the optimum condition for the curve579), and if then operating conditions change so that we commence tooperate on the curve 649 which passes through the point 533 but rises toa higher value of economy, the passing to the conditions of curve 649will not in and of itself result in setting the econometer intooperation to effect correction of speed necessary to avail ourselves ofthe possibly higher point of economy to which this new curve 649 risesas shown in FIGURE l. This statement is true, since without the.production of a change of speed the economy of the operation willcontinue to be indicated by the elevation of the point 583, which pointis mutual to both of the curves 579 and 49. I have, therefore, madeprovision to institute corrective actions in all cases including thosesuch as I have just described. This provision I shall now explain:

If periodically the motor 557 be brought into action for a shortinterval of time, sufficient to effect a slight change of operatingconditions (e.g., power-motor .present equipment.

speed), then the position of the finger 587 will be periodicallyslightly altered, sufficiently to institute any necessary correctiveoperations, and to ensure in any case that we are `always seeking abetter or more efficient overall operating condition. To this end, inFIGURE 2, I have shown the small shunt motor 650, cut directly acrossthe source of direct current but under control of the switch 651, whichsmall motor operates at substantially constant speed, and is in effect amore or less accurate timer. This motor drives a rotary contactor 652 atslow speed, to effect a circuit closing operation, say every fiveminutes for an interval of a few seconds, by reason of engagement of therotary contact 653 with the stationary contact 654. These contacts 653and 654 are bridged across the relay contacts of FIGURE 2, so thatwhenever this rotary contact functions it supplies current directly tothe motor 557 for such short interval, say five or a few seconds, andthen cuts current off from such motor. But that amount of motoroperation will effect such slight change of operating conditions as willinstitute operation of the Econometer, and correction will then continueand be carried through in the normal manner by the circuits of FIGURE 2.

In connection with the foregoing it is also to be noted that in thenormal operation of the Econometer of FIG- URE 2 the direction ofoperation of the motor 557 is always such that the economy was rising toand slightly past the point of optimum conditions when the circuit wasbroken `at the contact 593; and further that the final circuit openingof the scheme of FIGURE 2 always takes place at the contact 593, leavingthe reversing switch 603 unchanged. Therefore when the timer nextfunctions in its periodical operations it will cause the motor 557 tooperate in the same corrective direction as before, until thereaftersome condition shall arise requiring reversal of such motor.

It is of course evident that the curves of overall efficiency or economyentering into the foregoing discussions and disclosures of mechanisms ormeans can be drawn to relate the efficiency or economy to any selectedvariable of operating functions which is controllable by the operator,whether such control actually be made by the operator or not. Thus,while I have shown the curves of FIGURE 1 as showing eficiency oreconomy related to propeller speed as the controllable variable oroperating function, they might have been shown as efficiency or economyrelated to propeller blade pitch as the controllable variable oroperating function. Such and other alternative combinations of theoperations of the Econometer with elements of the airplane driving andcontrol devi-ces have been shown in the figures by way of illustrationof combinations and uses of the devices to which the present applicationrelates, but not by way of limitation of the coverage to be afforded bythe patent to be issued on this case.

It is also noted that the elements of the present invention do notoperate by examination of any such curves, but only by sensing ofeffects produced by changes of operating conditions produced by numerousvariables, with provision for then effecting corrections of the selectedvariable which is directly under lcontrol of the The references to theseveral curves have therefore been especially for the purpose of betterexplaining the relative effects lproduced by the elements of the meansherein disclosed and claimed.

Reference is now made to FIGURES 3 and 4 as illustrative of two airplanecontrols with which the present invention may be used, as follows:

In FIGURE 3 I have shown schematically an arrangement for securingcomplete control of the several functions automatically and by manualsetting of the principal controls of the airplanes power plant. In thisfigure I have shown the control board having the control handles 427 forpower-motor speed and 428 for freefiight air speed, the same workingover the scales 429 and 430 suitably marked. Also in this case I haveshown the four propeller hubs 519, 520, 521 and 522, the same beingprovided with the electrical blade pitch control devices, comprising thesets of polyphase wound elements (stator and rotor), including thestator elements 527 (secured to the hubs), and the rotor elements 527a(rotatably mounted in said stators, and geared to the blade pitchchanging studs). Said propeller hubs are also provided with the sliprings 529, 530, 531, 532, 533 and 534, on the propeller shafts 528; andthe power-motors 523, 524, 525 and 526 for the respective propellersdrive said shafts in understood and conventional manner. There are alsoshown the respective small polyphase generators 535 for these units,driven from the shafts 528 proportionately to motor speed, and connectedto the slip rings 532, 533 and 534 by the lines 538.

This showing also includes the unit 492 comprising a small polyphasegenerator driven proportionately to freeairspeed of the airplane by asmall fan so that the frequency of current delivered over the lines54,1a from such unit 492 is a measure of the actual air-speed ofairplane dight at all times in normal operation. This embodiment alsoincludes the motor-generator unit 457 which may be controlled as tospeed by the setting of the handle 428, so that the frequency ofpolyphase current supplied over the lines 463 is a measure of the setspeed for free-Hight; and this embodiment also includes the polyphasedifferential unit 50S similar to the corresponding unit of otherembodiments shown in the aforesaid Letters Patent No. 2,794,507 issuedJune 4, 1957, and of which Serial No. 662,542, now Patent No. 3,096,469(being the parent of the present application) was a division. Thus theshaft of this unit 508 will turn in the one direction or the otheraccording to the relative frequencies delivered by the units 457 and492, to thereby set the finger `512 against either of the contacts 513or 514 or centrally of said contacts, as dictated by the relativefrequencies aforesaid.

The embodiment of FIGURE 3 also includes the unit 433 comprising a motorgenerator unit whose speed can be controlled by field control, throughthe medium of the fork 440441 operated by the handle 427. Thus thenormal setting of power-motor speed is dictated by the setting of theyhandle 427, and by the polyphase lines 539 leading to the slip rings529, 530 and 531 of the respective propellerblade shifting units.

In the present embodiment I have provided a distinct unit 545 forcontrol of power delivered by the various power-motor units of engines523, 524, 525 and 526, by throttle control, and in synchronized fashion,preferably by use of such control as that shown, for example, in FIGURES18 and 20 of Letters Patent of the United States No. 2,612,956, issuedto me October 7, 1952, and previously referred to herein. That is tosay, the polyphase lines 546 from the small generator of this unit 545lead to the throttle power control units 50 of FIGURES 18 and 20 of saidPatent No. 2,612,956, so that the setting of the speed of themotor-generator unit 545 is a measure of power to be delivered by eachof the powermotors, and with all said power-motors synchronized as tosuch power delivery. In other words with any given setting of therotative speed of this unit 545 the power called for delivery by each`power-motor will be maintained at a given value, and this also meansthat the conditions of rotative speed and torque demanded by thepropeller of such power-motor must be maintained such as to absorb thisamount of power, if stable conditions of operation are to be maintained.

Likewise, by varying the setting (speed) of the unit 545 from time totime we shall also be able to vary the power developed by the severalpower-motors (while maintaining them in synchronism as to such power),so that varying requirements for power shall be automatically suppliedand complied with at all times.

Now the rotative speed of this unit 545 is controlled by the demand forpower `as dictated bythe setting of the handle 428 for free-flight speed(except under certain special conditions), so that by setting the handle42S for the desired free-iiight-speed we shall automatically maintainthe power developed by the several power-motors at the amount needed tomaintain that speed, and with varying conditions of operation, such asrising and descending of the airplane, changes of altitude, etc., thepower developed from time to time will automatically re-adjust itself tomaintain that pre-set speed of flight, until the setting of the handle428 is altered, or until manual control intervenes, or some otherspecial condition is applied. To accomplish the foregoing results thefollowing arrangements have been provided:

The rheostat 547 for the field control of the shunt motor 548 of theunit 545 is controlled by the small reversible motor 549, through theworm gear and rack and pinion arrangement 550. This small motor 549 hasthe two fields 551 and 552 which may be alternately used in series withthe motor armature, to enable reversal of said armature in wellunderstood manner. These fields 551 and 552 are connected to thecontacts 513 and 514 of the unit 508, so that as the actual free-flightspeed of the airplane either exceeds or is less than the indicatedspeedsetting of the handle 428 the frequency of the motor generator unit545 will be raised or lowered as the case may be, to therebycorrespondingly adjust the powers being delivered by the severalpower-motors by throttle control thereof, and under synchronism of suchpowers. In other words, although the handle 428 is set to a givenfree-iight-speed, still the result thereof is to adjust and controlpowers developed by the several power-motors to meet the demand forpower as found by the controls, in order to maintain that speed offree-flight.

During the foregoing adjustments of power as dictated by the setting ofthe handle 42S and the instaneous actual free-iiight-speed conditions,as found by the unit 492 in comparison to the setting of the handle 427(for powermotor rotative speed), the rotative speeds of the severalpower-motors will be maintained in synchronism and control by theseveral units 535 in comparison to the frequency delivered by the unit433 over the lines 539, and by use of the polyphase units 527-527 in therespective propeller hubs, all as heretofore explained. Thus speeds ofrotation of the several propellers and power-motors will be controlledautomatically while powers are adjusted from time to time to maintainfree-flight-speed constant at the setting of the handle 428.

Now manifestly with this arrangement the varying demands for powerneeded to maintain desired 4free-flight conditions will be met byadjustments of the blade pitches, since speeds are being maintainedconstant under setting of the handle 427. This condition, however, haslimitations, since increasing demand for power due to some condition ofight, in order to maintain free-flight-speed, must be met by increasedpitches of the blades. It is well known that increase of pitch (angle ofattack) results in increased traction or pull up to a certain criticalangle, after which further increase of such pitch angle results in rapiddecrease of traction or pull. Manifestly, therefore, increased powerdemands (at given rotative speed) can be met only up to a certain pointby increase of pitch, after which any further increase in demanded powercan be met only by increase of rotative speed, without further increasein pitch.

In operation usually the handle 427 will be set for that rotative speedof the power-motors which is proper for take-off and the free-flightconditions requiring rotative speed comparable to the rotative speedused during takeoff. Any higher rotative speeds of the motors, requiredduring iiight will have to be met either by manual re-setting of thehandle 427 or by some form of automatic control related to the controlsso far disclosed herein. In the type of blade shifting device hereinreferred to as being contained within the propeller hub, and which isoperated by the rotor 527a working in reaction to the stator 527,

there is usually provided a segmental gear 553 which is turned `forblade pitch changes by the rotor 527fL through a large gear reduction,so that a fraction of one complete rotation of such segmental gear willresult in complete setting of the blades from one extreme of pitch tothe other. As a simple means of securing supplemental rotative speedcontrol for the power-motors to meet conditions imposed when highpitches or angles of blades have been met, I have shown the contact 554carried by each of these segmental -gears 553, and swinging back andforth with changes of blade pitch. I have also shown the contacts 555and 556 at the two sides of said swinging contact 554, so that as saidcontact 554 moves back and forth it will engage either of the contacts555 or 556 as the case may be, at the corresponding limit of swing ofthe companion segmental contact carrier 553. Thus, if increase of pitchshould be indicated by clock-wise rotation of the segmental gear 553,when the pitch reaches a certain high value, the contact 554 will engagethe contact 555, whereas when the pitch reaches a certain low value thecontact 554 will engage the contact 556, having previously disengagedfrom the contact 555. Normally the clearance between the contacts 555and 556 is such that normal adjustments of pitch under control of theunit 527-527a will not result in engagement of the contact 554 witheither o-f the contacts 555 or 556, so that normally the speedadjustments are effected entirely by the reactions between the elements527 and 5273, and are of relatively small amount, merely to maintainsynchronism, or to maintain free-iiight-speed at the pre-set value asshown by the setting of the handle 427.

There is provided the small reversible series motor 557 for the unit433, same including the field coils 55S and 559 of opposite winding, sothat by exciting either one of these coils the direction of motorrotation is controlled. This motor 557 acts on the contact carrier 560for the rheostat Stil of the unit 433 in manner similar to the motor 444of FIGURE 18 of said Letters Patent No. 2,794,507. That is to say, whenthe contact carrier has been set to any given setting by the handle 427(for rotative speed), by excitation of either one or the other of thefield coils S53 or 559 the setting of the contact carrier may beincreased to that for a higher rotative speed, without change of handlesetting, and thereafter the contact carrier be again reset to theposition of the handle setting, all due to the frictional drive betweenthe worm gear reduction of the motor 557 and the rack bar of the Contactcarrier itself, as more fully disclosed in the said Letters Patent No.2,794,507.

I provide a direct current line 562 leading to the several contactelements 554; and I also provide the lines 563 and 56e leading from thecontacts 555 and 556 respectively to the terminals of the field coils558 and 559. Thus, whenever any one of the blade pitch controls reachesthe high pitch position of its contact 555 the eld coil 558 of the motor557 will be energized, causing the rheostat 561 to be cut in to a higherresistance and causing increase of frequency delivered by t-he unit 433,and over the lines 539 to the several blade pitch control devices, andresulting in increase of power-motor speed. This will result in finallyre-setting the pitches of the propellers `back to a slightly lowerangle, so that the contacts `554 will be drawn away from the contacts555 and further resetting of the speed of the unit 433 will cease. Thenthe power-motor speed, and the speeds of the propellers will be retainedat the new setting, higher than the indication of the handle 427, untila further time. Likewise movement of the contacts 554 incounter-clockwise direction will result in re-setting of the speed ofthe unit 433 to a lower value, until finally it is re-set at the valueindicated by the setting of the handle 427.

It is noted that with very high velocities of free-flight, as of 400 or500 or even 600 miles per hour, the velocity of the setting of thehandle 427 for take-off will generally be considerably less than thatdesired for such free-flight speeds, but this condition will be fullytaken care of by 21 the provision of the segmental rotative speedcontrol just above explained.

It should also be noted that if desired an interconnection might beprovided between the two control handles 427 `and 428, similar to thoseillustrated in FIGURES 12, 13 and 14, of said Letters Patent No.2,794,507, so that settings of the handle 428 for high velocities offree-flight -would be automatically accomplished by proper settings ofthe handle 427 for corresponding rotational rates of the power-motors,thereby avoiding the necessity of automatic control of the resetting ofthe unit 433 as just above expl'ained.

It is also here noted that if desired the contacts S55 of the embodimentshown in FIGURE 3 might be made angularly adjusta-ble so that the actualblade angle at which said contacts should become effective could beadjusted. Thus, with increase of free-flight velocity said contactscould bel set to higher angle positions, since, manifestly, withincrease of velocity of free-flight the actual blade angles should beincreased in order to maintain the desired angle of attack. For example,when operating at 500 miles per hour free-flight velocity the actualangle should be greater (for a given angle of attack), and fordevelopment of a desired reaction against the air, than for a conditionof 400 miles per hour. Still the momentary adjustments of pitch should'be effected close to this greater actual angle than at the lowervelocities of free-flight, in order to maintain control of engine speedat the new rotational rate, and to maintain synchronism at the newrotational rate. In other words, the unit 527-527a would then functionwithin a close range of adjustments at this greater angle setting.

In the arrangement shown in FIGURE 4 the unit 545 serves to contro] andsynchronize the power-motors for speed by throttle control instead of byblade pitch control as in the embodiment shown in FIGURE 3. Thisthrottle control is made over the lines 546, and according to thedisclosures of FIGURES l, 17 and 19 of my previously mentioned LettersPatent of the United States No. 2,612,956. In the present embodiment thehandle 428 serves to control the unit 457 which determines thefreeflight velocity, working through the differential 508; but in thepresentcase this differential controls the reversible motor 548 forcontrol of the propeller blade-pitches as a group or gang. This is doneby the control of the pressure reducing valve 659, of the type shown inFIGURES 6 and 7 of my aforesaid Letters Patent No. 2,794,507; and theblade shifting devices 660 are of the type shown in FIGURES 3, 4 and 5of said Letters Patent, or Iother suitable type. It isrnoted that withthis arrangement the synchronization of the power-motors for speed iseffected by throttle control thereof.

In both of FIGURES 3 and 4 of this case the unit 545 is used forthrottle control but, as disclosed in my aforesaid Letters Patent No.2,794,507 other arrangements embodying the econometer unit and whicharrangements effect the controls by blade-pitch may be used. I do notintend to limit myself to throttle controls except as I may do so in theclaims to follow.

In the foregoing disclosures it will be seen that in an operationwherein a power producing medium is us'ed to produce a function whichvaries from time to time, and wherein the production of said function isdependent on at least one variable which is controllable as to itsamount, and wherein the ratio at any given time between the amount ofsuch function which is produced, as compared to the amount of such powerproducing medium depends on the value of such controllable variable, andwherein said ratio under such conditions has a maximum value for a givenvalue of the controllable variable, I have provided means toautomatically change the value of the controllable Variable from time totime, so that said ratio is brought substantially to such maximum amountby such automatic change is made. It will also be seen that I haveprovided such automatic means which may function in substantiallycontinuous manner to effect changes in the value of the controllablevariable in substantially continuous manner, or periodically atregularly time intervals. It will also be seen that specifically I haveprovided means to effect changes in such controllable variable whereinthe power producing medium comprises fuel which is consumed, and whereinthe amount of the function which is produced may be either at asubstantially constant rate or at a variable rate. Other specificfeatures will also be apparent from study of said disclosures.

Continuing the above analysis, in the above statement the powerproducing medium is the fuel, the function produced is the air speed,the element at least one variable in the embodiments shown in thedrawings is either the motor throttle or the blade-pitch, the amount ofsuch function is the value of the air speed or other power consumingrate in mph. or other selected units of speed, and the amount of suchpower producing medium is the rate of fuel feed. Specifically, in FIGURE3 the element at least one variable is the control effected by the motorthrottle, and in FIGURE 4- it is the propeller blade pitch. It isevident, however, that when using the econometer feature of the presentinvention the operation might be other than production of power, andthat the variable might be other than a motor throttle or a blade pitchcontrol, that the power producing medium might be other than fuel, thatthe function produced might be other than air speed, and the amountthereof might be other than mph. or other suitable units, and that theamount of power producing medium might be other than the rate of fuelfeed. There are various industrial uses and operations wherein thefunctions and the variables and the end products or results are suchthat the devices embodying my present invention might be usefullyapplied.

It is also noted that the motor 557 is in effect a servomotor actingunder proper control to effect the changes or controls which are desiredin the operations of the element to which such servo-motor is drivinglyconnected, but that in some cases a servo-motor as a special elementmight be found unnecessary, the operations which it produces in theembodiments herein illustrated being then performed by other means orelements.

It is also evident that in its broader aspects the present inventiondoes not require the use of a ratio determining device such asillustrated in FIGURE 2 which acts to subtract logarithms of functionalvalues from each other, but instead there might be substituted any othersuitable form of ratio determining device to compare the amount of suchfunction produced with the amount of such power producing medium, orequivalent functions or values or amounts. Accordingly, I do not intendto limit myself except as I may do so in the claims to follow.

For clarity of understanding of the sequence of the signals andoperations produced by the specific embodiments shown in FIGURES 3 and4, I have also included the Flow Sheets shown in FIGURES 5 and 6,corresponding to said FIGURES 3 and 4, respectively. These FIGURES 5 and6 carry numerals and legends corresponding to those of FIGURES 3 and 4,so that it is not deemed necessary to describe such FIGURES 5 and 6 infull detail. It is, however, not'ed that in each case, being thethrottle control shown in FIGURES 3 and 4, and in FIGURES 5 and 6, andthe propeller pitch controls shown in said figures, are brought into thearrangements in such manner that runaway conditions cannot occur. Thus,in FIGURE 3 the econometer controls the propeller pitch, with throttlecontrol by the differential of manually preset flight-speed compared tothe actual airflight speed, whereas in FIGURE 4 the econometer controlsthe throttle, with propeller pitch control by the differential betweenmanually pre-set flight-speed and the actual airflight speed. But ineach case the operation of the Eoono meter is based on the ratio betweenrate of ffight and rate 23 of fuel consumption. This is made clear bythe flowsheets of FIGURES and 6.

I claim:

1. Means to generate and transform and deliver power to perform afunction and to control the economy of such power transformation anddelivery, comprising in combination a fuel consuming prime mover unit,means to control the rate of fuel input to said unit, means to transformand deliver the power from said prime mover unit and to perform saidpower delivery function at a determined rate of delivery, the rate offuel input control means comprising a first power control means and themeans to transform and deliver the power from the prime mover unitcomprising a second power control means, means to produce a firstfrequency at rate proportional to the rate of delivery of the function,means to produce a second frequency at rate proportional to the rate offuel input to the fuel consuming prime mover unit, ratio determiningmeans to compare the values of the first and second frequencies,operative connections between the first frequency producing means andthe ratio determining means, and operative connections between thesecond frequency producing means and the ratio determining means, saidratio determining means including a ratio indicating element movable ina first defined direction corresponding to increasing ratio values andmovable in a second defined direction corresponding to decreasing ratiovalues, a reversible servo-motor unit, operative connections between theservo-motor unit and the power control means first defined effective toactuate said first defined power control means for increase or decreaseof the rate controlled by said first defined power control meansaccording to direction of movement of said servo-motor unit, andoperative connections between the ratio indicating element of the ratiodetermining means and said servomotor unit, said operative connectionsbetween the ratio indicating element of the ratio determining means andthe power control means first defined, including means constituted tocause the servo-motor unit to function in direction to actuate the saidfirst defined power control means for change of the ratio determined bysaid power control means to produce movement of the ratio indicatingelement in the increasing ratio indicating direction.

2. Means as defined in claim 1, wherein the operative connections fromthe servo-motor unit are to the first defined power control means.

3. Means as defined in claim 1, wherein the operative connections fromthe servo-motor unit are to the second defined power control means.

4. Means as defined in claim 1, wherein the ratio indicating elementmovement changes from the first defined direction to the second defineddirection corresponding to some position of the first defined powercontrol means wherein the operative connections between the ratioindicating element of the ratio determining means and said servo-motorunit include means to discontinue functioning of the servo-motor unitwhen the ratio indicating element movement changes direction from saidfirst defined direction to said second defined direction.

5. Means as defined in claim 4, wherein the operative connectionsbetween the ratio indicating element of the ratio determining means andsaid servo-motor unit also include means to cause the servo-motor unitto function when the ratio indicating element moves in said seconddefined direction.

6. Means as defined in claim 5, wherein the operative connectionsbetween the ratio indicating element of the ratio determining means andsaid servo-motor unit also include servo-motor reversing means, andwherein said connections also include servo-motor reverser actuatingmeans and include means to cause said reverser actuating means tofunction when the ratio indicating element of the ratio determiningmeans moves in said second defined direction more than a pre-determinedminimal amount.

7. Means as defined in claim 1, together with a continuously operatingtimer unit, and operative connections between said timer unit and theservo-motor effective to deliver sustained timed impulses to theservomotor unit including means to actuate said servo-motor unit apredetermined time interval corresponding to each sustained impulse.

8. Means to generate and transform and deliver power to perform afunction and to control the economy of such power transformation anddelivery, comprising in combination a fuel consuming prime mover unit,means to control the rate of fuel input to said unit, means to transformand deliver the power from said prime mover unit to perform saidfunction, the control means for the rate of fuel input comprising afirst power control means, and the means to transform and deliver thepower from the prime mover unit comprising a second power control means,first response means constituted to produce a measurable first responseeffect of value proportional to the rate of delivery of the function,second response means constituted to produce a second measurableresponse effect of value proportional to the rate of fuel input to thefuel consuming prime mover unit, ratio determining means to compare thevalues of the first and second measurable response effects, operativeconnections between the first response means and the ratio determiningmeans, operative connections between said second response means and theratio determining means, the value of said ratio varying as the powercontrolled by one of the power control means changes, and the firstderivative of said ratio including a change between positive andnegative incremental values at some value of the power controlled bysaid power control means, said ratio determining means including a ratioindicating element movable in a first defined direction corresponding toincreasing ratio values and movable in a second defined directioncorresponding to decreasing ratio values, and operative means connectingthe ratio indicating element with that power control means whose changecauses variation of the value of the ratio, constituted to cause saidpower control means to effect its control in direction to cause theratio indicated by the ratio indicating means to increase, and todiscontinue the change of said last named power control means when theincremental value of the first derivative of the ratio changes signbetween a negative and a positive quantity.

9. Means as defined in claim 8, wherein the power control means whosechange causes variation of the value of the ratio, comprises the meansto control the rate of fuel input to the fuel consuming prime moverunit.

10. Means as defined in claim 8, wherein the power control means whosechange causes variation of the value of the ratio, comprises the meansto transform and deliver the power from the prime mover unit to performthe function.

No references cited.

ISADOR WEIL, Primary Examiner.

CLARENCE R. GORDON, Examiner.

1. MEANS TO GENERATE AND TRANSFORM AND DELIVER POWER TO PERFORM AFUNCTION AND TO CONTROL THE ECONOMY OF SUCH POWER TRANSFORMATION ANDDELIVERY, COMPRISING IN COMBINATION A FUEL CONSUMING PRIME MOVER UNIT,MEANS TO CONTROL THE RATE OF FUEL INPUT TO SAID UNIT, MEANS TO TRANSFORMAND DELIVER THE POWER FROM SAID PRIME MOVER UNIT AND TO PERFORM SAIDPOWER DELIVERY FUNCTION AT A DETERMINED RATE OF DELIVERY, THE RATE OFFUEL INPUT CONTROL MEANS COMPRISING A FIRST POWER CONTROL MEANS AND THEMEANS TO TRANSFORM AND DELIVER THE POWER FROM THE PRIME MOVER UNITCOMPRISING A SECOND POWER CONTROL MEANS, MEANS TO PRODUCE A FIRSTFREQUENCY AT RATE PROPORTIONAL TO THE RATE OF DELIVERY OF THE FUNCTION,MEANS TO PRODUCE A SECOND FREQUENCY AT RATE PROPORTIONAL TO THE RATE OFFUEL INPUT TO THE FUEL CONSUMING PRIME MOVER UNIT, RATIO DETERMININGMEANS TO COMPARE THE VALUES OF THE FIRST AND SECOND FREQUENCIES,OPERATIVE CONNECTIONS BETWEEN THE FIRST FREQUENCY PRODUCING MEANS ANDTHE RATIO DETERMINING MEANS, AND OPERATIVE CONNECTIONS BETWEEN THESECOND FREQUENCY PRODUCING MEANS AND THE RATIO DETERMINING MEANS, SAIDRATIO DETERMINING MEANS INCLUDING A RATIO INDICATING ELEMENT MOVABLE INA FIRST DEFINED DIRECTION CORRESPONDING TO INCREASING RATIO VALUES ANDMOVABLE IN A SECOND DEFINED DIRECTION CORRESPONDING TO DECREASING RATIOVALUES, A REVERSIBLE SERVO-MOTOR UNIT, OPERATIVE CONNECTIONS BETWEEN THESERVO-MOTOR UNIT AND THE POWER CONTROL MEANS FIRST DEFINED EFFECTIVE TOACTUATE SAID FIRST DEFINED POWER CONTROL MEANS FOR INCREASE OR DECREASEOF THE RATE CONTROLLED BY SAID FIRST DEFINED POWER CONTROL MEANSACCORDING TO DIRECTION OF MOVEMENT OF SAID SERVO-MOTOR UNIT, ANDOPERATIVE CONNECTIONS BETWEEN THE RATIO INDICATING ELEMENT OF THE RADIODETERMINING MEANS AND SAID SERVOMOTOR UNIT, SAID OPERATIVE CONNECTIONSBETWEEN THE RATIO INDICATING ELEMENT OF THE RATIO DETERMINING MEANS ANDTHE POWER CONTROL MEANS FIRST DEFINED, INCLUDING MEANS CONSTITUTED TOCAUSE THE SERVO-MOTOR UNIT TO FUNCTION IN DIRECTION TO ACTUATE THE SAIDFIRST DEFINED POWER CONTROL MEANS FOR CHANGE OF THE RATIO DETERMINED BYSAID POWER CONTROL MEANS TO PRODUCE MOVEMENT OFF THE RATIO INDICATINGELEMENT IN THE INCREASING RATIO INDICATING DIRECTION.